JPH1128596A - Die for forming powder in warm-state - Google Patents

Abstract

PROBLEM TO BE SOLVED: To save the electric power consumption needed by a heater for heating a die and to prevent the thermal expansion caused by rising of the temp. of a die plate. SOLUTION: In a withdrawal system die device provided with the heater 25 for heating the die 21, the die 21 is fixed into the inner hole of a die case 28 fitted to the die plate 23 through a heat-insulating material 20. Further, a cooling tube 29a between the die case 28 and the heat-insulating material 20, and a cooling tube 29b between the die plate 23 and the die case 28, are arranged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a mold apparatus for warm powder molding.

[0002]

2. Description of the Related Art An iron-based metal powder containing a special lubricant is used for 15 times.
It is known that when heated to a temperature of about 0 ° C. and compressed, a compact having a higher density can be obtained than when compacted by an ordinary method, and is used for manufacturing sintered machine parts.
One of the apparatuses used for this powder molding is a withdrawal type apparatus. FIG. 3 is a longitudinal sectional view showing the basic structure.

In FIG. 1, rod-shaped heaters 16 and 25 are attached to the upper punch 13 and the die 21, respectively, and the current to the heaters 16 and 25 is adjusted while measuring the temperature with a thermometer (not shown). Adjust so that the temperature around the molding cavity becomes appropriate. Further, using a shuttle feeder provided with a heating means, metal powder is filled by a usual method, compressed by upper and lower punches, and then extracted from the die 21.

In the conventional molding apparatus shown in FIG. 3, the upper punch plate 10, the die plate 23, the base plate 40
Are different from each other, between the guide post 14 and the bearing 24, and between the guide rod 60 and the bearing 41 of the base plate 40, creaking, galling, or abnormal wear occurs, leading to a decrease in accuracy of the molding apparatus, and There is a problem that the life is shortened, and it has been desired to solve them.

[0005] In order to solve this problem, the present applicant has proposed in Japanese Patent Application No. 8-93507 a molding apparatus having a structure as shown in FIGS. In FIG. 4, a cooling pipe 29 is provided between the die 21 and the die plate 23, and the die plate receiving plate 26 is provided on the lower surface of the die plate 23 via the gap A and the heat insulating means by the heat insulating material 27.
The guide rod 60 is fixed to the die plate receiving plate 26, and the guide post 14 is fixed to the die plate receiving plate 26 in a state of being unrelated to the die plate 23. FIG. 5 shows the cooling pipe 29.
Instead, the outer periphery and upper end surface of the die 21 are covered with a heat insulating material 20 such as a fluororesin or zirconia.

In the molding apparatus having such a configuration, the die plate 23 and the guide post 14 are not connected to each other, and the temperature rise of the die plate receiving plate 26 to which the guide post 14 and the guide rod 60 are fixed or fitted is controlled. As a result, the thermal expansion of the upper punch plate 10, the die plate receiving plate 26, the guide post 14 of the base plate 40, or the thermal expansion of the guide rod 60 becomes substantially the same, resulting in bearings 24 and 41. There is no increase in unbalanced load or radial load with respect to, and wear can be reduced.

[0007]

However, in the structure shown in FIG. 4, if a large amount of cooling water flows through the cooling pipe 29 in order to lower the temperature of the die plate 23, the temperature of the die 21 is also lowered. That is, the amount of power applied to the heater 25 increases. On the other hand, in the structure shown in FIG. 5, since the means for suppressing heat conduction is only the heat insulating material, the die plate receiving plate 26
Since the temperature does not decrease so much, it is inevitable that squeezing occurs in the bearing portion and hinder the improvement of the molding speed.

[0008]

SUMMARY OF THE INVENTION In order to solve these problems, according to the present invention, there is provided a mold for warm powder molding of a draw-drawal type provided with a heater for heating a die of a mold. The die 21 is fixed to the inner hole of the die case 28 via the heat insulating material 20, and a cooling pipe 29 a is provided between the die case 28 and the heat insulating material 20 and a cooling pipe 29 b is provided between the die plate 23 and the die case 28. Provide. In this powder molding die, the outer cooling pipe 2
The temperature of the cooling medium supplied to the inner cooling pipe 29a is set to the normal temperature while the temperature of the cooling medium supplied to the inner cooling pipe 29a is set to the normal temperature.
b. The temperature is higher than the temperature of the cooling medium and lower than the temperature of the die.

[0009]

FIG. 1 shows a cross-sectional structure around a die. The die plate 23 is supported by a guide rod 60, and the guide post 14 is supported by a bearing 24 in the same manner as the structure of the conventional mold. A ring-shaped electric heater 25 is provided at the lower end of the die 21. Die 21
Is made of cemented carbide, the thermal conductivity is relatively good, so that the temperature difference of the entire die case 28 can be reduced. Controlling the heater current with a thermometer (not shown) is the same as in the prior art.

The outer periphery of the die 21 is covered with a ring of the heat insulating material 20. The heat insulating material 20 has only to have a low thermal conductivity and a certain level of mechanical strength and heat resistance, but is most preferably made of zirconia. The die 21 and the heat insulating material 20 are joined to each other and fixed to the inner hole of the die case 28 to form a unit. A spiral groove communicating with the cooling pipe 29a is formed on the inner surface of the die case 28, and the heat insulating material 20 is press-fitted or fitted to form a flow path for a coolant such as water. Flow the refrigerant in the direction of the arrow inside. The refrigerant is water or oil. The temperature of the refrigerant varies depending on the size of the mold apparatus, but is lower than the temperature of the die 21 and higher than room temperature, and is about 50 to 90 ° C. This refrigerant is preheated in a reserve tank (not shown) and pumped by a pump. Although FIG. 2 shows an example in which the die 21 and the heat insulating material 20 are press-fitted, it is easier to assemble by fitting and using a refrigerant leak-proof seal.

The cooling pipe 29 is also provided on the inner surface of the die plate 23.
b, and a spiral groove communicating with the heat insulating material 2 is formed.
0 and when the unit of the die case 28 is attached,
A coolant flow path is formed, and the coolant is supplied in the direction of the arrow in the figure. The temperature and flow rate of the refrigerant vary depending on the size of the mold apparatus, but are close to room temperature of about 10 to 25 ° C. so that the temperature of the die plate 23 is substantially the same as the temperature of the base plate 40 or the upper punch plate 10. Use a relatively low temperature and change the flow rate as appropriate.

The die 21 of the mold apparatus having such a structure is as follows.
It is uniformly heated by the heater 25 provided below. Since the heat insulating material 20 is provided outside the die 21, heat conduction in the lateral direction is suppressed. The outside of the heat insulating material 20 is cooled by a refrigerant having a temperature lower than the temperature of the die 21 but relatively high,
Although the heat insulating material 20 is cooled relatively strongly, the temperature of the die 21 is not deprived and the power consumption of the heater 25 is not increased. In addition, the temperature of the surrounding die case 28 is also reduced to some extent. The temperature of the die case 28 is intermediate between the temperature of the die 21 and the normal temperature, and the temperature conducted from the die case 28 by the cooling means (cooling pipe 29b) outside the die case 28 can be discharged out of the system. This prevents the temperature of the outer die plate 23 from rising.

FIG. 2 is a graph showing the temperature distribution in the lateral direction of the die set. The solid line A shows the case of the mold apparatus of the present invention shown in FIG. 1, the chain line B shows the case of the conventional apparatus shown in FIG. 4, and the broken line C shows the case of the conventional apparatus shown in FIG. Each is a test example in which the die 21 was heated to 150 ° C. Water at a temperature of 25 ° C. was passed through the cooling pipe 29 of the apparatus indicated by the dashed line B and the cooling pipe outside the apparatus indicated by the solid line A, and hot water at a temperature of 90 ° C. was passed through the cooling pipe inside the apparatus indicated by the solid line A. In the device indicated by the broken line C, the temperature near the guide post 14 is 90 ° C. In the device of the chain line B, the ambient temperature is about 90 ° C. by the cooling pipe 29, and the temperature near the guide post 14 is about 7 ° C.
0 ° C. In order to further lower the temperature, the temperature of the cooling medium may be lowered to increase the flow rate.
5, the required power amount increases. In the device shown by the solid line A, the heat conduction is suppressed by the heat insulating material 20, the average temperature of the die case 28 is about 100 ° C. by the hot water cooling inside, and the die case 28 of about 100 ° C. is cooled by the outside cooling. The tube was water-cooled, and the entire die plate reached about 30 ° C. This indicates that the thermal expansion of the lateral member is suppressed.

[0014]

As described above, the warm forming mold according to the present invention can suppress the heat conduction by the heat insulating material around the die,
By using a cooling structure that sequentially lowers the temperature in two stages from the higher temperature side, the increase in power consumption required for the heater of the die is reduced, and the temperature of the die plate rises to cause thermal expansion. According to this mold, there is no creaking or damage to the mold, so that the efficiency of powder molding can be improved.

[Brief description of the drawings]

FIG. 1 is a partial longitudinal sectional view of a warm powder molding die of the present invention.

FIG. 2 is a graph showing temperature distributions of the mold of the present invention and a conventional mold.

FIG. 3 is a longitudinal sectional view of a conventional mold.

FIG. 4 is a partial longitudinal sectional view of an improved conventional mold.

FIG. 5 is a partial longitudinal sectional view of another conventional improved mold.

[Explanation of symbols]

 14 Guide Post 20 Heat Insulation Material 21 Die 23 Die Plate 24 Bearing 25 Heater 28 Die Case 29a, 29b Cooling Tube 60 Guide Rod

Claims (2)

[Claims] 1. A withdrawal-type mold apparatus provided with a heater for heating a mold die.
3, the die 21 is fixed to the inner hole of the die case 28 via the heat insulating material 20, the cooling pipe 29a is provided between the die case 28 and the heat insulating material 20, and the die plate 23 and the die case 28 are fixed. A mold for warm powder molding, wherein a cooling pipe 29b is provided between the molds. 2. The temperature of the cooling medium supplied to the outer cooling pipe 29b is normal temperature, the temperature of the cooling medium supplied to the inner cooling pipe 29a is higher than the temperature of the cooling medium of the cooling pipe 29b, and 21. A temperature lower than the temperature of 21.
3. The mold for warm powder molding according to 1.).